Reduction of azo compounds.



UNITED STATES PATENT FFICE;

MAX BUCHNERyOF MANNI-IEIM, GERMANY.

REDUCTION OF AZO COMPOUNDS.

SPECIFICATION forming part of Letters Patent No. 700,671, dated May 20, 1902.

Application filed September 24,1900. Serial No. 30,966- (No specimens.)

To all whom it may concern:

Be it known that LMAX B UCHNER, a citizen of the Empire of Germany, residing at Mannheim, in the Empire of Germany, have inventprocess of reducing nitro compounds to the corresponding amines by means of electro lytic action used in connection with a tin cathode or of an indifferent cathode and anelectrolytic fluid containing tin, the process consisting, more specifically, in introducing the nitro bodies dissolved or suspended in hydrochloric acid into the cathode-space of an electrolytic cell and submitting the same to action of the current. I have found in the course of subsequent experiments that this treatment may be applied also forthe purpose of reducing azo compounds. In this case, however, it is desirable to first coat the tin or indifferent cathode with a layer of tin sponge to maintain an elevated temperature, preferably about 60 centigrade, in the cathodespace and to operate with lower current densities than indicated in the aforesaid application.

It is to be observed that the preparation of the cathode may be dispensed with if at the beginning of electrolysis a relatively small quantity of electrolytically-precipitated powdered tin is added to the electrolytic fiuid.

My invention therefore, broadly considered, consists in passing an electrolytic current through an azo body dissolved or suspended in an electrolytic fluid in the presence of tin, and more specifically in the use in connection therewith of an addition of tin to the tin or indifferent cathode and of an elevated temperature.

My invention, moreover, comprises such further features as will be hereinafter described and pointed out in the claims.

To enable those skilled in the art to carry out my invention, I will now describe the same in detailby reciting the following examples, which constitute what I consider the preferable embodiment of the same.

Example 1-Reduction ofpara-cm'zido-azobenzol to paraphenylene-(Z'iamine.-An electrolytic cell is divided into an anode and a cathode space by a suitable diaphragm, as will be readily understood. A ten-percent. solution of sulfuric acid is poured into the anodespace,and anode of indifferent anode material, such as lead, is introduced. Into the cathodecompartment I pour a mixture consisting of 48.7 parts,by weight,of chlorid of para-amidoazo-benzol, five grams of powdered electrolytically -precipitated tin dissolved or suspended in one hundred parts, by volume, of Water and two hundred and fifty parts, by volume, of fuming hydrochloric acid. An electric current is then passed through a tin or indifferent cathode. The liquid mixture is vigorously agitated or stirred during the course of the electrolysis,whose completion is indicated by the commencement of an active evolution of hydrogen. The current employed is preferably of a density of three hundred to four hundred amperes per square meter, and the temperature employed in the cathode-space is advantageously 60 centigrade. Theresultingparaphenylene-diamine is precipitated in the form of a chlorid by saturating the cathode electrolyte with hydrochloric-acid gas in the cold, the anilin, which is produced at the sametime, remaining in solution.

Example 2 Re(luction of orange II to amz'do-beta-naphthoL-The same arrangement of electrolytic cell and the same materials for the anode-space as in Example 1 are-employed in this case. I charge the oathode compartment with a mixture of thirtythree parts, by weight, of orange II, two hundred and fifty parts, by weight, of water and two hundred and fifty parts, by weight, of fuming hydrochloric acid. I also add a quantity of powdered tin, as in the first example, if an indifferent cathode is employed, and, in general, conduct the operation as in said example. Even if a tin cathode is employed dispensable. The amido-beta-naphthol produced under these conditions is isolated and purified. according to well-known methods.

What I claim, and desire to secure by Letters Patent of the United States, is

1. The process of reducing azo compounds which consists in passing an electric current through such azo compounds dissolved or suspended in an electrolytic fluid capable of dissolving tin in the presence of tin, the azo compound and tin being arranged in the cathode-compartment.

2. The process of reducing azo compounds which consists in passing an electric current through such azo compounds dissolved or suspended in an electrolytic fluid containing tin, the azo compound and tin being arranged in the cathode-compartment.

3. The process of reducing azo compounds which consists in passing an electric current through such 'azo compounds dissolved or suspended in an electrolytic fluid capable of dissolving tin in the presence of tin and at an elevated temperature, the electrolytic fluid being capable of dissolving tin and the tin 6. The process of reducing azo compounds which consists in charging the cathode-space of an electrolytic cell with a mixture of the azo compound and powdered tin with water and hydrochloric acid and then passing the electrolytic current through the mixture.

In testimony whereof I affix my signature in presence of two witnesses.

MAX BUCHNER.

l/Vitnesses:

JACOB ADRIAN, FRITZ A011. 

